HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Holographic4. Modify/create a new 32-bit DWORD value named
FirstRunSucceeded. Set the value date to 1 to add
Mixed Reality to Settings. Set it to 0 if you wish to remove it. (If you're using Windows 10-64 bit, you still need to create a 32-bit DWORD value.)

5. Restart your PC and go to the Settings app. If you set the DWORD value to
0, Mixed Reality should be gone.